Three-dimensional (3D) printers employ a method of feeding plastic filament into a heated nozzle, which then deposits a bead of softened plastic, using Cartesian x-y-z motion, to build a thin layer of plastic. The extent of the layer is determined using software, which slices a solid computer model into thin layers. Each layer is progressively “printed” and built on top of the previous layer, until the complete solid model is realized as solid plastic.